---
id: terminology
title: Terminology
sidebar_label: Terminology
slug: /api/master/terminology
---

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Master stations typically communicate with multiple outstations over multiple communication channels. We'll describe in the following sections how you can create different channel types, each of which can be used to talk to multiple outstations on the channel.

## MasterChannel

You can create a `MasterChannel` using generic configuration combined with transport-specific options. Once created, all channel instances have the same API,
regardless of the underlying transport.

## Association

The DNP3 standard defines an association as "a representation of a logical connection between a master and an outstation". In this library, you add an association to a `MasterChannel` to enable communication with a particular outstation address. Adding an association to a channel will return an `AssociationId`, which can then be used in conjunction with the channel to perform actions on that outstation.

```mermaid
graph TD
A[MasterChannel] --association #1--> B[Outstation #1]
A --association #2--> C[Outstation #2]
```

:::note
It's typical to just have one association per channel over TCP. However, it's also possible to encounter virtual outstations on a single TCP endpoint. Serial channels are frequently part of a multi-drop network where a single serial channel is used to communicate with multiple independent outstations.
:::






